A method for preparing perfluoropolyether surfactants by microchannel method

Abstract

The present invention provides a method for preparing perfluoropolyether surfactants by a microchannel method, and relates to the field of preparation of fluorine fine chemicals. The method of the present invention comprises the following steps: in the presence of a fluorocarbon solvent, perfluoropropylene and oxygen undergo a liquid phase oxidation reaction to obtain an oxidized crude product; the oxidized crude product is separated by distillation to obtain a perfluoropolyether; the perfluoropolyether and pure water are continuously hydrolyzed in a microchannel reaction device to obtain a hydrolyzate; the hydrolyzate is sequentially subjected to gas-liquid separation and liquid phase stratification to obtain the perfluoropolyether carboxylic acid; the perfluoropolyether carboxylic acid is mixed with an alkali solution, and a neutralization reaction is performed to obtain the perfluoropolyether surfactant. The present invention uses a microchannel reactor continuous method to prepare a perfluoropolyether surfactant from the perfluoropropylene oxidation product perfluoropolyether, which has the advantages of efficient mass and heat transfer, avoiding temperature runaway, stable reaction, safety and reliability, and easy industrial scale-up.

Description

Technical Field

[0001] The invention relates to the field of preparation of fluorine fine chemicals, and in particular to a method for preparing perfluoropolyether surfactants by a microchannel method. Background Art

[0002] Fluorosurfactant is a kind of special surfactant, which has the characteristics of "three highs" and "two hates", and is widely used in synthetic detergents, cosmetics, food, rubber, plastics, photosensitive materials, inks and other industries. The main chain of the fluorinated polyether surfactant molecule contains ether bonds. The oxygen atoms on the ether bonds, on the one hand, make the Krafft point of fluorinated polyether surfactants mostly lower than 0°C due to their softness, thus greatly improving the solubility of the surfactant; on the other hand, it helps the biodegradation of fluorinated polyether surfactants and can eliminate their residues in organisms and the natural environment. Therefore, fluorinated polyether surfactants are a kind of high-efficiency and environmentally friendly products.

[0003] CN115286782A discloses a sodium perfluoropolyether carboxylate and a method thereof, wherein hexafluoropropylene (HFP), oxygen, carbonyl fluoride (COF 2 ) is introduced with a fluorine-containing solvent, and then a perfluoropolyether carboxylic acid solution is obtained through photo-oxidation and light-irradiation reaction, and then a hydrolysis and neutralization reaction is carried out to prepare a sodium perfluoropolyether carboxylate solution. CN114031762A discloses a method of obtaining a perfluoropolyether surfactant by using HFP, chlorotrifluoroethylene and oxygen as raw materials, and sequentially undergoing photo-oxidation, monomer recovery, de-peroxygenation, distillation, hydrolysis, washing and neutralization. Both methods use hexafluoropropylene as the main raw material and require specific ultraviolet light and extremely low temperature restrictions to react. In addition, in order to remove the peroxidized polymer produced in the reaction during the reaction, a high temperature (80~300℃) treatment is carried out again, which increases the complexity and danger of the process.

[0004] In the process of producing hexafluoropropylene oxide (HFPO) by continuous liquid phase reaction of hexafluoropropylene (HFP) and molecular oxygen, complicated side reactions occur. The conversion rate of hexafluoropropylene can reach over 90%, but the yield of HFPO is only 50-80%, and the by-product COF 2 CF 3 COF and perfluoropolyether. At present, these perfluoropolyethers are treated by adding excessive alkali for neutralization or incineration, which seriously causes economic losses and environmental pollution. In addition, since the kettle hydrolysis process of perfluoropolyether is violent and has a high risk factor, the highly toxic hydrogen fluoride generated is easily released into the gas phase of the container or the atmosphere, which is very likely to cause accidents such as overpressure, bursting disc rupture and environmental pollution, which is not conducive to industrial expansion.

[0005] Therefore, there is an urgent need to provide a method for producing perfluoropolyether surfactants that is more stable, safe, reliable, and easy to scale up industrially.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing perfluoropolyether surfactants by a microchannel method. The method uses a microchannel reactor to continuously prepare perfluoropolyether, a product of perfluoropropylene oxidation, into a perfluoropolyether surfactant, and has the advantages of efficient mass and heat transfer, avoiding runaway temperature, stable reaction, safety and reliability, and easy industrial scale-up.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] In a first aspect, the present invention provides a method for preparing a perfluoropolyether surfactant by a microchannel method, the method comprising the following steps:

[0010] In the presence of a fluorocarbon solvent, perfluoropropylene and oxygen undergo a liquid phase oxidation reaction to obtain a crude oxidation product; the crude oxidation product is separated by distillation to obtain a perfluoropolyether;

[0011] The perfluoropolyether and pure water are continuously hydrolyzed in a microchannel reaction device to obtain a hydrolysis product; the hydrolysis product is sequentially subjected to gas-liquid separation and liquid phase separation to obtain the perfluoropolyether carboxylic acid;

[0012] The perfluoropolyether carboxylic acid and alkaline solution are mixed and neutralized to obtain the perfluoropolyether surfactant; wherein the structural formula of the perfluoropolyether surfactant is as follows:

[0013] CF 3 O(CF 2 O) m CF 2 COOX

[0014] Wherein, X is selected from Na, K or NH 4 Any one of the above, m is selected from an integer between 0 and 10, preferably an integer between 3 and 10. The perfluoropolyether surfactant can be used as a dispersant in the dispersion polymerization of fluorinated monomers such as TFE, CTFE, ETFE, PVF, HFP, and PFA, replacing toxic and non-environmentally friendly surfactants such as PFOA.

[0015] Preferably, the molar ratio of perfluoropropylene to oxygen is (0.5-3.0):1, preferably (1-2.5).

[0016] Preferably, the ratio of the mass of the fluorocarbon solvent to the total mass of the perfluoropropylene and oxygen is (4-12):1, preferably (6-10):1.

[0017] Preferably, the fluorocarbon solvent comprises a hydrofluoroalkane (C a H b F 2a-b ), perfluoroalkane (C a F 2a+2 ), perfluoroether (C a F 2a+2 O c ) or a combination of at least two of them; wherein a≥3, a, b, c are all integers.

[0018] Preferably, the fluorocarbon solvent is HFC227ea and / or HFC236fa.

[0019] Preferably, the temperature of the liquid phase oxidation reaction is 90-160°C, preferably 120-160°C.

[0020] Preferably, the pressure of the liquid phase oxidation reaction is 2-6 MPa, preferably 2-5 MPa.

[0021] Preferably, the liquid phase oxidation reaction time is 0.5 to 4 h, preferably 1 to 3 h.

[0022] Preferably, the distillation separation method includes any one of vacuum distillation, atmospheric distillation or pressure distillation, or a combination of at least two of them.

[0023] Preferably, the crude oxidation product is separated by distillation to obtain the following four components in sequence:

[0024] The first component is a mixture of carbonyl fluoride and perfluoroacetyl fluoride;

[0025] The second component is hexafluoropropylene oxide;

[0026] The third component is a fluorocarbon solvent;

[0027] The fourth component is the perfluoropolyether.

[0028] Preferably, the fluorocarbon solvent of the third component is recyclable and / or reusable, has a boiling point higher than HFPO and lower than perfluoropolyether, and is a non-ozone depleting substance.

[0029] Preferably, in the process of separating and obtaining the fourth component, the absolute pressure of the vacuum distillation is 10-100 kPa, and the bottom temperature is 70-180°C.

[0030] Preferably, the perfluoropolyether comprises a perfluoropolyether represented by formula A and / or a perfluoropolyether represented by formula B:

[0031] CF 3 O(CF 2 O) p COF: Formula A

[0032] CF 3 O(CF 2 O) q CF 2 COF: Formula B

[0033] Wherein, p is selected from an integer between 0 and 10, and q is selected from an integer between 0 and 10.

[0034] Preferably, the mass ratio of the perfluoropolyether to pure water is (1-5):(1-5), preferably (1-2):(1-5).

[0035] Preferably, the residence time of the hydrolysis is 20 s to 10 min.

[0036] Preferably, the hydrolysis temperature is 20-90°C.

[0037] Preferably, the hydrolysis pressure is 0.1-1.0 MPa.

[0038] Preferably, the gas-liquid separation comprises:

[0039] The hydrolysis product enters a gas-liquid separation device, and undergoes gas-liquid separation to obtain a gas phase product and a liquid phase product; wherein the gas phase product includes carbon dioxide and hydrogen fluoride, and the liquid phase product includes hydrofluoric acid and perfluoropolyether carboxylic acid.

[0040] Preferably, the pressure of the gas-liquid separation is 0.2~1.0 MPa.

[0041] Preferably, the gas phase product is absorbed via alkaline solution.

[0042] Wherein, the concentration of the alkali solution is 0.5~3 M; the solute in the alkali solution is selected from sodium hydroxide and / or potassium hydroxide.

[0043] Preferably, the liquid phase stratification comprises:

[0044] In the gas-liquid separation device, the liquid phase product obtained by gas-liquid separation is allowed to stand for stratification to obtain an aqueous phase and an organic phase; wherein the aqueous phase comprises hydrofluoric acid, and the organic phase comprises perfluoropolyether carboxylic acid.

[0045] Preferably, the aqueous phase is further filtered to obtain hydrofluoric acid.

[0046] Preferably, the organic phase is further washed with water to obtain perfluoropolyether carboxylic acid.

[0047] Preferably, the water washing treatment is performed three times or more.

[0048] Preferably, the pH of the hydrolysis is 9-11.

[0049] Preferably, the solute in the alkali solution is selected from any one of sodium hydroxide, potassium hydroxide or ammonia, or a combination of at least two of them; and the solvent in the alkali solution is selected from water.

[0050] Preferably, the temperature of the neutralization reaction is 60-90°C.

[0051] Preferably, the neutralization reaction time is 5 to 30 min.

[0052] Preferably, the neutralization reaction is carried out under stirring, and the stirring speed is 50-300 rpm.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The method of the present invention fully utilizes the perfluoropolyether produced as a by-product of perfluoropropylene oxidation, improves the atomic utilization rate of the raw materials, reduces the additional cost and environmental pollution of by-product treatment, and improves the economic benefits of industrial production.

[0055] (2) The present invention adopts liquid phase oxidation of perfluoropropylene to prepare HFPO. The oxidation reaction temperature can directly decompose the peroxide polymer. Therefore, the by-product perfluoropolyether does not contain peroxide polymer and does not require further high temperature or ultraviolet light irradiation treatment. It has the advantages of simple process, low risk and low consumption.

[0056] (3) The present invention adopts a microchannel reactor to continuously hydrolyze perfluoropolyether, and obtains high-value-added perfluoropolyether surfactants and by-product hydrofluoric acid through gas-liquid separation and liquid-liquid stratification. It has the advantages of efficient mass and heat transfer, avoidance of temperature runaway, stable reaction, safety and reliability, and easy industrial scale-up. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 The present invention is a flow chart of the method for preparing perfluoropolyether surfactants by the microchannel method.

[0059] Among them, R1 represents a liquid phase oxidation reaction device, R2 represents a microchannel reaction device, and R3 represents a neutralization reaction device. DETAILED DESCRIPTION

[0060] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0061] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0062] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0063] It should be noted that specific details are described in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0064] In a first aspect, the present invention provides a method for preparing a perfluoropolyether surfactant by a microchannel method, such as Figure 1 As shown, the method comprises the following steps:

[0065] (1) Preparation of perfluoropolyether: In the presence of a fluorocarbon solvent, perfluoropropylene and oxygen undergo a liquid phase oxidation reaction to obtain a crude oxidation product; the crude oxidation product is separated by distillation to obtain a perfluoropolyether;

[0066] (2) Preparing perfluoropolyether carboxylic acid: continuously hydrolyzing the perfluoropolyether and water in a microchannel reaction device to obtain a hydrolysis product; and sequentially performing gas-liquid separation and liquid phase separation on the hydrolysis product to obtain the perfluoropolyether carboxylic acid;

[0067] (3) preparing a perfluoropolyether surfactant: mixing the perfluoropolyether carboxylic acid and an alkali solution, and performing a neutralization reaction to obtain the perfluoropolyether surfactant;

[0068] Wherein, the structural formula of the perfluoropolyether surfactant is as follows:

[0069] CF 3 O(CF 2 O) m CF 2 COOX.

[0070] As an optional embodiment, X is selected from Na, K or NH 4 Any one of .

[0071] As an optional embodiment, m is selected from an integer between 0 and 10, for example, it can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, preferably an integer between 3 and 10.

[0072] In the present invention, the method for preparing the perfluoropolyether surfactant is to produce HFPO by HFP molecular oxygen liquid phase oxidation method and produce perfluoropolyether at the same time, and the perfluoropolyether purified by continuous hydrolysis and rectification is used in a microchannel reactor, and the hydrolyzed material is separated in a gas-liquid separator to obtain perfluoropolyether carboxylic acid, and further reacted with alkali to obtain a high value-added perfluoropolyether surfactant. The method has the advantages of high raw material atomic utilization, high economic benefit, safety and reliability, and easy industrial scale-up.

[0073] As an optional embodiment, in step (1), the molar ratio of perfluoropropylene to oxygen is (0.5-3.0):1, for example, it can be 0.5:1, 0.6:1, 0.8:1, 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3.0:1, etc., preferably (1-2.5).

[0074] As an optional embodiment, in step (1), the ratio of the mass of the fluorocarbon solvent to the total mass of the perfluoropropylene and oxygen is (4-12):1, for example, it can be 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, 10:1, 10.5:1, 11:1, 11.5:1, 12:1, etc., preferably (6-10):1.

[0075] As an optional embodiment, in step (1), the fluorocarbon solvent includes hydrofluoroalkane (C a H b F 2a-b ), perfluoroalkane (Ca F 2a+2 ), perfluoroether (C a F 2a+2 O c ) or a combination of at least two thereof; wherein a≥3, a, b, c are all integers, preferably HFC227ea and / or HFC236fa.

[0076] As an optional embodiment, in step (1), the temperature of the liquid phase oxidation reaction is 90-160°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 160°C, etc., preferably 120-160°C.

[0077] As an optional embodiment, in step (1), the pressure of the liquid phase oxidation reaction is 2-6 MPa, for example, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, etc., preferably 2-5 MPa.

[0078] As an optional embodiment, in step (1), the liquid phase oxidation reaction time is 0.5 to 4 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc., preferably 1 to 3 h.

[0079] It should be noted that if the reaction temperature is too low during the liquid phase oxidation reaction of perfluoropropylene and oxygen in step (1), peroxide polymers will be generated, which may cause explosion; if the reaction pressure is too low, the solubility of the material is poor, resulting in low conversion rate and yield. Furthermore, the reaction conditions may even affect the structural form of perfluoropolyether and produce branched perfluoropolyether.

[0080] As an optional embodiment, in step (1), the distillation separation method includes any one of vacuum distillation, atmospheric distillation or pressure distillation, or a combination of at least two of them.

[0081] As an optional embodiment, in step (1), the crude oxidation product is separated by distillation to obtain the following four components in sequence:

[0082] The first component is a mixture of carbonyl fluoride and perfluoroacetyl fluoride;

[0083] The second component is hexafluoropropylene oxide;

[0084] The third component is a fluorocarbon solvent;

[0085] The fourth component is the perfluoropolyether.

[0086] It should be noted that perfluoropolyether surfactants made from low-boiling point short-chain perfluoropolyethers have poor performance, while perfluoropolyethers made from high-boiling point long-chains require harsh equipment conditions and have high energy consumption costs.

[0087] As an optional embodiment, in step (1), in the process of separating the first component, the distillation pressure is 0.8-1.8 MPa, for example, it can be 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, etc., and the bottom temperature is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc.

[0088] As an optional embodiment, in step (1), in the process of separating the second component, the distillation pressure is 0.1-1 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, etc., and the bottom temperature is 40-60°C, for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc.

[0089] It should be noted that in the process of separating the third component, since the third component is a fluorocarbon solvent, and the fluorocarbon solvent includes but is not limited to hydrofluoroalkanes (C a H b F 2a-b ), perfluoroalkane (C a F 2a+2 ), perfluoroether (C a F 2a+2 O c ), so in the specific process of distilling out the third component (fluorocarbon solvent), it is necessary to set the distillation pressure and temperature range according to the specific selected fluorocarbon solvent type.

[0090] As an optional embodiment, in step (1), taking HFC236fa as the third component (fluorocarbon solvent) as an example, in the process of separating the third component, the distillation pressure is 0.05-0.8 MPa, for example, it can be 0.05 MPa, 0.08 MPa, 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, etc., and the bottom temperature is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, etc.

[0091] As an optional embodiment, in step (1), the fluorocarbon solvent of the third component can be recovered and / or reused, has a boiling point higher than HFPO and lower than perfluoropolyether, and is a non-ozone depleting substance.

[0092] As an optional embodiment, in step (1), in the process of separating the fourth component, the absolute pressure of the vacuum distillation is 10-100 kPa, for example, it can be 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, 100 kPa, etc., and the bottom temperature is 70-180°C, for example, it can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc.

[0093] As an optional embodiment, in step (1), the perfluoropolyether includes a perfluoropolyether represented by formula A and / or a perfluoropolyether represented by formula B:

[0094] CF 3 O(CF 2 O) p COF: Formula A

[0095] CF 3 O(CF 2 O) q CF 2 COF: Formula B

[0096] Wherein, p is selected from an integer between 0 and 10, and q is selected from an integer between 0 and 10.

[0097] As an optional implementation, p is selected from an integer between 0 and 10, for example, it can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0098] As an optional implementation, q is selected from an integer between 0 and 10, for example, it can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0099] As an optional implementation, in step (2), the material of the microchannel reaction device includes silicon carbide and / or Hastelloy.

[0100] It should be noted that in step (2), hydrogen fluoride will be produced during the continuous hydrolysis of perfluoropolyether and water in the microchannel reaction device; therefore, the material of the microchannel is preferably corrosion-resistant silicon carbide or Hastelloy.

[0101] As an optional embodiment, in step (2), the mass ratio of the perfluoropolyether to water is (1-5):(1-5), for example, it can be 5:1, 4:1, 3:1, 2:1, 1:1, 5:2, 3:2, 1:1, 5:3, 4:3, 2:3, 1:3, 5:4, 3:4, 1:2, 1:4, 4:5, 3:5, 2:5, 1:5, etc., preferably (1-2):(1-5).

[0102] As an optional embodiment, in step (2), the residence time of the hydrolysis is 20 s to 10 min, for example, it can be 20 s, 30 s, 40 s, 50 s, 60 s, 1.2 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5min, 10 min, etc.

[0103] As an optional embodiment, in step (2), the hydrolysis temperature is 20-90°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0104] As an optional embodiment, in step (2), the hydrolysis pressure is 0.1-1.0 MPa, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, etc.

[0105] It should be noted that in the process of continuous hydrolysis of perfluoropolyether and water in the microchannel reaction device in step (2), the mass ratio of perfluoropolyether to pure water, residence time, temperature and pressure will affect the hydrolysis conversion rate of perfluoropolyether and the concentration of by-product hydrofluoric acid.

[0106] It should be noted that in step (2), the gas-liquid separation device can be used to separate the gaseous carbon dioxide produced by the continuous hydrolysis in the microchannel, and to separate the aqueous phase hydrofluoric acid and the organic phase perfluoropolyether carboxylic acid in the liquid phase.

[0107] As an optional embodiment, in step (2), the gas-liquid separation includes:

[0108] The hydrolysis product enters a gas-liquid separation device, and undergoes gas-liquid separation to obtain a gas phase product and a liquid phase product; wherein the gas phase product includes carbon dioxide and hydrogen fluoride, and the liquid phase product includes hydrofluoric acid and perfluoropolyether carboxylic acid.

[0109] As an optional embodiment, in step (2), the pressure of the gas-liquid separation is 0.2-1.0 MPa, for example, it can be 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, etc.

[0110] As an optional embodiment, in step (2), the gas phase product obtained by the gas-liquid separation is absorbed by alkaline solution.

[0111] As an optional embodiment, in step (2), the concentration of the alkaline solution used to absorb the gas phase product (carbon dioxide) is 0.5~3 M, for example, it can be 0.5 M, 0.6 M, 0.8 M, 1.0 M, 1.2 M, 1.4 M, 1.6 M, 1.8 M, 2 M, 2.2 M, 2.4 M, 2.6 M, 2.8 M, 3 M, etc.

[0112] As an optional embodiment, in step (2), the solute in the alkaline solution used to absorb the gas phase product (carbon dioxide) is selected from sodium hydroxide and / or potassium hydroxide.

[0113] As an optional embodiment, in step (2), the liquid phase stratification includes:

[0114] In the gas-liquid separation device, the liquid phase product obtained by gas-liquid separation is allowed to stand for stratification to obtain an aqueous phase and an organic phase; wherein the aqueous phase comprises hydrofluoric acid, and the organic phase comprises perfluoropolyether carboxylic acid.

[0115] As an optional implementation, in step (2), the aqueous phase is further filtered to obtain hydrofluoric acid.

[0116] As an optional embodiment, in step (2), the organic phase is further washed with water to obtain perfluoropolyether carboxylic acid.

[0117] As an optional embodiment, in step (2), the water washing treatment is performed three times or more, for example, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, etc.

[0118] It should be noted that the purpose of further washing with water in step (2) of the present invention is mainly to remove a small amount of hydrofluoric acid in the perfluoropolyether carboxylic acid.

[0119] As an optional embodiment, in step (3), the pH of the hydrolysis is 9 to 11, for example, it can be 9, 9.5, 10, 10.5, 11, etc.

[0120] As an optional embodiment, in step (3), the solute in the alkali solution is selected from any one of sodium hydroxide, potassium hydroxide or ammonia, or a combination of at least two of them; and the solvent in the alkali solution is selected from water.

[0121] As an optional embodiment, in step (3), the alkaline solution includes any one of an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide or aqueous ammonia, or a combination of at least two of them.

[0122] As an optional embodiment, in step (3), the temperature of the neutralization reaction is 60-90°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0123] As an optional embodiment, in step (3), the neutralization reaction time is 5 to 30 min, for example, it can be 5 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, etc.

[0124] As an optional embodiment, in step (3), the neutralization reaction is carried out under stirring, and the stirring speed is 50-300 rpm, for example, it can be 50 rpm, 60 rpm, 80 rpm, 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, etc.

[0125] In the present invention, the perfluoropolyether represented by formula A is hydrolyzed to finally decompose into HF and CO 2 The perfluoropolyether shown in formula B is hydrolyzed to produce perfluoropolyether carboxylic acid CF3 O(CF 2 O) m CF 2 COOH is then neutralized with alkali solution to adjust the pH of the solution and finally obtain the perfluoropolyether surfactant CF 3 O(CF 2 O) m CF 2 COOX; wherein X is selected from Na, K or NH 4 Any one of, m is selected from an integer between 0 and 10.

[0126] The perfluoropolyether surfactant finally prepared by the present invention can be used as a dispersant in the dispersion polymerization of fluorinated monomers such as TFE, CTFE, PVF, HFP, PFA, etc., to replace toxic non-environmentally friendly surfactants such as PFOA. In addition, since the oxidation reaction temperature is relatively high, the perfluoropolyether of the oxidized crude product does not contain peroxide perfluoropolyether, and there is no need to consider the explosiveness of peroxide substances. Different oxidation conditions (the ratio of HFP to oxygen, reaction temperature, reaction pressure) will not only affect the yield of HFPO and perfluoropolyether, but also affect the content of the perfluoropolyether component, resulting in different molecular weights of perfluoropolyether carboxylic acids.

[0127] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0128] Example 1

[0129] This embodiment provides a method for preparing a perfluoropolyether surfactant by a microchannel method, the method comprising the following steps:

[0130] S1. Preparation of perfluoropolyether:

[0131] First, a fluorocarbon solvent (HFC236fa) and HFP are introduced into the liquid phase oxidation reaction device R1, and then oxygen is introduced, the molar ratio of HFP to oxygen is 2:1, and the mass ratio of the solvent to the total mass of HFP and oxygen is 6:1; the reaction pressure of the liquid phase oxidation reaction device R1 is 3.5 MPa, the temperature is 140°C, and the residence time is 2 h to obtain a crude oxidation product;

[0132] The crude oxidation product is separated in sequence by distillation to obtain the following four components: the first component is a mixture of carbonyl fluoride and perfluoroacetyl fluoride; the second component is HFPO; the third component is a fluorocarbon solvent; the fourth component is the perfluoropolyether; the yield of HFPO is 71.2%, and the yield of perfluoropolyether is 10.0%;

[0133] Among them, the first three components are separated by distillation. During the separation of the first component, the distillation pressure is 1.3 MPa and the bottom temperature is 70±2°C; during the separation of the second component, the distillation pressure is 0.5 MPa and the bottom temperature is 50±2°C; during the separation of the third component, the distillation pressure is 0.4 MPa and the bottom temperature is 55±2°C; during the separation of the fourth component perfluoropolyether, the absolute pressure of the vacuum distillation is 50 kPa and the bottom temperature is 140°C.

[0134] S2, preparation of perfluoropolyether carboxylic acid:

[0135] The perfluoropolyether separated from S1 and pure water were respectively introduced into the silicon carbide microchannel reaction device R2 for continuous hydrolysis, the mass ratio of perfluoropolyether to pure water was 1:1, the residence time was 3 min, the temperature was 30°C, and the pressure was 0.3 MPa to obtain a hydrolysis product;

[0136] The hydrolysis product is placed in a gas-liquid separator and allowed to stand for gas-liquid separation (separation pressure is 0.4 MPa) to obtain a gas phase product and a liquid phase product; wherein the gas phase product includes carbon dioxide and hydrogen fluoride, and the liquid phase product includes hydrofluoric acid and perfluoropolyether carboxylic acid;

[0137] In the gas-liquid separation device, the liquid phase product obtained by gas-liquid separation is allowed to stand for stratification to obtain an aqueous phase and an organic phase; wherein the aqueous phase includes hydrofluoric acid with a concentration of 31 wt %; wherein the organic phase is washed with water 4 times to obtain a perfluoropolyether carboxylic acid (structural formula: CF 3 O(CF 2 O) q CF 2 COONa, molecular weight 403);

[0138] The gas phase product obtained by gas-liquid separation is passed into alkaline solution for absorption; wherein the alkaline solution is a 1 M aqueous solution of sodium hydroxide.

[0139] S3, preparation of perfluoropolyether surfactant:

[0140] Perfluoropolyether carboxylic acid and 10 wt% NaOH solution were placed in a neutralization reaction device R3 and stirred for neutralization. The neutralization reaction temperature was 70°C, the reaction time was 10 min, the rotation speed was 200 rpm, and the pH was 10, thereby obtaining a perfluoropolyether surfactant.

[0141] Example 2

[0142] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Embodiment 1 only in that, in S1, the molar ratio of HFP to oxygen is 3:1, and other settings are completely consistent with Embodiment 1.

[0143] Example 3

[0144] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method. The only difference from Example 1 is that in S1, the pressure of the liquid phase oxidation reaction is 2.5 MPa and the temperature is 135°C. Other settings are exactly the same as in Example 1.

[0145] Example 4

[0146] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Embodiment 1 only in that, in S1, the bottom temperature of the perfluoropolyether distillation tower is 160° C., and other settings are completely consistent with Embodiment 1.

[0147] Example 5

[0148] This embodiment provides a method for preparing a perfluoropolyether surfactant by a microchannel method, the method comprising the following steps:

[0149] S1. Preparation of perfluoropolyether:

[0150] First, a fluorocarbon solvent (HFC236fa) and HFP are introduced into the liquid phase oxidation reaction device R1, and then oxygen is introduced, the molar ratio of HFP to oxygen is 2:1, and the mass ratio of the solvent to the total mass of HFP and oxygen is 6:1; the reaction pressure of the liquid phase oxidation reaction device R1 is 3.5 MPa, the temperature is 140°C, and the residence time is 2 h to obtain a crude oxidation product;

[0151] The crude oxidation product is separated in sequence by distillation to obtain the following four components: the first component is a mixture of carbonyl fluoride and perfluoroacetyl fluoride; the second component is HFPO; the third component is a fluorocarbon solvent; the fourth component is the perfluoropolyether; the yield of HFPO is 71%, and the yield of perfluoropolyether is 10.2%;

[0152] Among them, the first three components are separated by distillation. During the separation of the first component, the distillation pressure is 1.3 MPa and the bottom temperature is 70±2°C; during the separation of the second component, the distillation pressure is 0.5 MPa and the bottom temperature is 50±2°C; during the separation of the third component, the distillation pressure is 0.4 MPa and the bottom temperature is 55±2°C; during the separation of the fourth component, the absolute pressure of the vacuum distillation is 50 kPa and the bottom temperature is 160°C.

[0153] S2, preparation of perfluoropolyether carboxylic acid:

[0154] The perfluoropolyether separated from S1 and pure water were respectively introduced into the silicon carbide microchannel reaction device R2 for continuous hydrolysis, the mass ratio of perfluoropolyether to pure water was 1:1, the residence time was 3 min, the temperature was 30°C, and the pressure was 0.3 MPa to obtain a hydrolysis product;

[0155] The hydrolysis product is placed in a gas-liquid separator and allowed to stand for gas-liquid separation (separation pressure is 0.7 MPa) to obtain a gas phase product and a liquid phase product; wherein the gas phase product includes carbon dioxide and hydrogen fluoride, and the liquid phase product includes hydrofluoric acid and perfluoropolyether carboxylic acid;

[0156] In the gas-liquid separation device, the liquid phase product obtained by gas-liquid separation is allowed to stand for stratification to obtain an aqueous phase and an organic phase; wherein the aqueous phase includes hydrofluoric acid with a concentration of 30 wt%; wherein the organic phase is washed with water three times to obtain a perfluoropolyether carboxylic acid (structural formula: CF 3 O(CF 2 O) q CF 2 COONa, molecular weight 411);

[0157] The gas phase product obtained by gas-liquid separation is passed into alkaline solution for absorption; wherein the alkaline solution is a 1 M aqueous solution of sodium hydroxide.

[0158] S3, preparation of perfluoropolyether surfactant:

[0159] Perfluoropolyether carboxylic acid and 10 wt% NaOH solution were placed in a neutralization reaction device R3 and stirred for neutralization. The neutralization reaction temperature was 65°C, the reaction time was 10 min, the rotation speed was 200 rpm, and the pH was 10, thereby obtaining a perfluoropolyether surfactant.

[0160] Example 6

[0161] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Embodiment 5 only in that in S2, the mass ratio of perfluoropolyether to pure water is 1.2:1, and other settings are exactly the same as Embodiment 5.

[0162] Example 7

[0163] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Embodiment 5 only in that in S2, the mass ratio of perfluoropolyether to pure water is 1.4:1, and other settings are exactly the same as Embodiment 5.

[0164] Example 8

[0165] This embodiment provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Embodiment 7 only in that, in S3, perfluoropolyether carboxylic acid and 10 wt% ammonia solution are neutralized in a reaction device R3, and other settings are exactly the same as Embodiment 7.

[0166] Comparative Example 1

[0167] This comparative example provides a method for preparing perfluoropolyether surfactants by a microchannel method, which is different from Example 1 only in that the perfluoropolyether prepared by S1 is directly hydrolyzed in an intermittent tank reactor, and other settings are completely consistent with Example 1.

[0168] Perfluoropolyether is hydrolyzed in an intermittent reactor. The hydrolysis reaction is violent, the temperature rises rapidly and is difficult to control, reaching 100°C, and a large amount of hydrogen fluoride gas is produced. Under stirring conditions, the complete hydrolysis time is 4 hours.

[0169] Test Case

[0170] Test samples: perfluoropolyether surfactants prepared in Examples 1 to 8 and Comparative Example 1, and intermediate products of each step;

[0171] Test method: using 19 F NMR was used to detect the perfluorocarboxylic acid structure and calculate the average molecular weight of the perfluoropolyether carboxylic acid.

[0172] The test results are shown in Table 1 below:

[0173] Table 1

[0174]

[0175] As shown in Table 1, the present invention adopts liquid phase oxidation to prepare HFPO, and the oxidation reaction temperature can directly decompose the peroxide polymer, so the by-product perfluoropolyether does not contain peroxide polymer, and no further high temperature or ultraviolet light irradiation treatment is required, which has the advantages of simple process, low risk and low consumption. In addition, the present invention adopts a microchannel reactor continuous method to prepare perfluoropropylene oxidation product perfluoropolyether into perfluoropolyether carboxylic acid and perfluoropolyether surfactant, which has the advantages of efficient mass and heat transfer, avoiding temperature runaway, stable reaction, safety and reliability, and easy industrial scale-up.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing perfluoropolyether surfactants by a microchannel method, characterized in that: The method comprises the following steps: In the presence of a fluorocarbon solvent, perfluoropropylene and oxygen undergo a liquid phase oxidation reaction to obtain a crude oxidation product; the crude oxidation product is separated by distillation to obtain a perfluoropolyether; The perfluoropolyether is composed of a perfluoropolyether represented by formula A and a perfluoropolyether represented by formula B: CF3O(CF2O) p COF: Formula A CF3O(CF2O) q CF2COF: Formula B Wherein, p is selected from an integer between 0 and 10, and q is selected from an integer between 0 and 10; Wherein, the molar ratio of perfluoropropylene to oxygen is (0.5-3.0):1; the temperature of the liquid phase oxidation reaction is 120-160° C., and the pressure of the liquid phase oxidation reaction is 2-5 MPa; The crude oxidation product is separated by distillation to obtain the following four components in sequence: the first component is a mixture of carbonyl fluoride and perfluoroacetyl fluoride; the second component is hexafluoropropylene oxide; the third component is a fluorocarbon solvent; the fourth component is the perfluoropolyether; in the process of separating the fourth component, the absolute pressure of the vacuum distillation is 10-100 kPa, and the bottom temperature is 70-180°C; The perfluoropolyether and pure water are continuously hydrolyzed in a microchannel reaction device to obtain a hydrolysis product; the hydrolysis product is sequentially subjected to gas-liquid separation and liquid phase separation to obtain a perfluoropolyether carboxylic acid; the mass ratio of the perfluoropolyether and pure water is (1-2):(1-5); the residence time of the hydrolysis is 20 s-10 min; the temperature of the hydrolysis is 20-90° C.; the pressure of the hydrolysis is 0.1-1.0 MPa; The gas-liquid separation comprises: the hydrolysis product enters the gas-liquid separation device, undergoes gas-liquid separation, and obtains a gas phase product and a liquid phase product; wherein the gas phase product comprises carbon dioxide and hydrogen fluoride, and the liquid phase product comprises hydrofluoric acid and perfluoropolyether carboxylic acid; wherein the gas phase product is absorbed by alkaline solution; the liquid phase stratification comprises: in the gas-liquid separation device, the liquid phase product obtained by gas-liquid separation is allowed to stand for stratification to obtain an aqueous phase and an organic phase; wherein the aqueous phase comprises hydrofluoric acid, and the organic phase comprises perfluoropolyether carboxylic acid; The perfluoropolyether carboxylic acid and alkaline solution are mixed and neutralized to obtain the perfluoropolyether surfactant; wherein the structural formula of the perfluoropolyether surfactant is as follows: CF3O(CF2O) m CF2COOX; Wherein, X is selected from any one of Na, K or NH4, and m is selected from an integer between 0 and 10.

2. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The ratio of the mass of the fluorocarbon solvent to the total mass of the perfluoropropylene and oxygen is (4-12):1; The fluorocarbon solvent includes hydrofluoroalkane C a H b F 2a-b , Perfluoroalkane C a F 2a+2 , Perfluoroether C a F 2a+2 O c Any one or a combination of at least two of the following; wherein a≥3, a, b, and c are all integers.

3. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The liquid phase oxidation reaction time is 0.5 to 4 h.

4. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The distillation separation method includes any one of vacuum distillation, atmospheric distillation or pressure distillation, or a combination of at least two of them.

5. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The pressure of the gas-liquid separation is 0.2~1 MPa; Wherein, the concentration of the alkali solution is 0.5~3 M; the solute in the alkali solution is selected from sodium hydroxide and / or potassium hydroxide.

6. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The aqueous phase is further filtered to obtain hydrofluoric acid; And / or, the organic phase is further washed with water to obtain perfluoropolyether carboxylic acid; And / or, when the organic phase needs to be washed with water, the number of times of the water washing treatment is more than 3 times.

7. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The pH of the hydrolysis is 9-11; and / or the mass percentage of the solute in the alkali solution is 5-15%; And / or, the solute in the alkali solution is selected from any one of sodium hydroxide, potassium hydroxide or ammonia or a combination of at least two thereof; and the solvent in the alkali solution is selected from water.

8. The method for preparing perfluoropolyether surfactants by microchannel method according to claim 1, characterized in that: The temperature of the neutralization reaction is 60-90°C; And / or, the neutralization reaction time is 5 to 30 min; And / or, the neutralization reaction is carried out under stirring, and the stirring speed is 50-300 rpm.

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